Hydraulic transformer



0a. is, 1949.

J. c. HANNA HYDRAULIC TRANSFORMER 6 Sheets-Sheet 1 Filed June 10, 1946 Ij7ZU67Z/Z 0f JQ/Zm G Haram, wwgme%f Oct. 18, 1949. J, c, HANNA 2,484,884

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Patented Oct. 18, 1949 HYDRAULIC TRANSFORMER John 0. Hanna, Chicago,111., assignor to Hanna Engineering Works, Chicago, 111., a corporationof Illinois Application June 10, 1946, Serial N0. 675,566

12 Claims.

The invention relates to hydraulic pressure boosters and has referencein particular to an improved device of this character which willtransform a low pressure liquid into a high pressure liquid and whereinthe reduction, in volume of the high pressure liquid will be inverselyproportional to the increase in pressure.

An object of the invention is to provide a combination pump and motordevice of the difierential piston type which will operate on a liquid ofa low pressure to raise a predetermined portion of said low pressureliquid to a higher pressure, which will be compact, embodying a minimumof operating parts, and wherein said parts will be contained in a singleunit of leakproof construction.

Another object of the invention is to provide a hydraulic transformer ofthe character described which will incorporate a novel distributor valvefor controlling the flow of low pressure liquid to the differentialpiston which operates as a pump of constant displacement.

A more specific object resides in the provision of a hydraulictransformer incorporating a distributor valve of the rotating type andwhich valve is hydraulically balanced by the balanced oil pressureacting upon it.

Another object of the invention is to provide a hydraulic transformerwherein the selector or rotating distributor valve in controlling theflow of the low pressure liquid to the differential piston will producefour pumping strokes of said piston per revolution.

Another object is to provide an improved hydraulic transformerincorporating a rotating distributor valve which will require theminimum in power to rotate it since the same is hydraulically balancedand which transformer will deliver a constant flow of high pressureliquid, the volume of which compared to the volume of low pressureliquid entering the device will be inversely proportional to the boostin pressure.

With these and various other objects in view, the invention may consist.of certain novel features of construction and operation as will be morefully described and particularly pointed out in the specification,drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the invention, andwherein like reference characters are used to designate like parts-Figure 1 is a longitudinal sectional view taken substantially centrallyof the hydraulic transformer of the invention showing the rotarydistributor valve and the differential piston;

Figure 2 is a transverse sectional view taken substantially along line22 of Figure 1;

Figure 3 is a transverse sectional view taken substantially along line33 of Figure 1;

Figure 4 is an end view of the hydraulic transformer looking in thedirection of the arrows on line v l l of Figure 1;

Figure 5 is an end view of the auxiliary piston assembly;

Figure 6 is a longitudinal sectional view of the auxiliary pistonassembly;

Figure 7 is a schematic arrangement illustrating the operating parts ofthe present hydraulic transformer, their relation with each other, andthe complete hydraulic circuit for their operation;

Figure 8 is another view illustrating the arrangement of the variousdevices and their connection as may be required for a complete hydrauliccircuit for :the transformer; and

Figure '9 is a transverse sectional View taken substantially along line:B-9 of Figure 1.

Referring to the drawings, and in particular to Figures 1 and 8, thehydraulic transformer of the invention is shown as including a unitaryhousing Ill which contains all the operating parts of the device andwhich is composed of several units including a central unit ll, an inletunit l2, an outlet unit l3 and a bearing unit 14. The inlet and outletunit are bolted .to opposite sides of the central unit by the securingscrews 15 shown in Figures 2 and .3 and the bearing unit is secured toI2 by the screws "5, as shown in Figures 1 and 4.

The housing H) which operates as a pressure booster is connected in thehydraulic circuit as disclosed in Figure 8, wherein the reservoir isindicated by numeral l1 and the low pressure oil pump IB is suitablyassociated therewith as by being supported on top of the reservoir. Anoil inlet line 20 extends from within the reservoir H to the inlet sideof the pump l'8 which is driven by motor 2 I, the shaft 22 of the motorproviding a sprocket '23 and connecting with the shaft 24 back to thereservoir.

of the pump by means of the coupling unit 25. A relief valve 26 isconnected. in line 2'! from the pump and which supplies low pressure oilto the auxiliary piston assembly 25 to be described in detail as thedescription proceeds. The low pressure oil leaves the assembly 28 byline 31'] which comprises the inlet for the hydraulic transformer ii],the inlet line 3" connecting with Ill, as best shown in Figure l. Thehydraulic transformer is provided with two outlets, one a low pressureoutlet and the other a high pressure outlet. The former is indicated bythe line 31 and which returns the low pressure oil from the transformerThe high pressure line 32 leads from the outlet unit l3 of the hydraulictransformer, as clearly evident from Figure 1, and is provided with theT connection 33, one end of which is associated with the auxiliarypiston assembly 28.

The operating shaft 3 1- of the hydraulic transformer is provided withsprocket 35, Figure 8, and this sprocket is driven by sprocket "23 bymeans of an endless chain operatively connecting the said sprockets sothat the motor 2i com-- prises the source of power for the low pressurepump and the transformer and which two devices are driven in unison.

Shaft 35- is journalled by the bearing member 85 of the transformer, theball bearing assembly 35 being provided for substantially frictionlessrotation and the inner end of said shaft being reduced to form the key37 which interlocks with the adjacent end of the rotating distributorvalve 38. Said valve is cylindrical in general form and is suitablyjournalled for rotation by the housing it. At the inlet end of thedistributor valve an internal passage 45 is formed having openings 4|which communicate with the chamber 42 connecting with the inlet conduit3|] so that low pressure oil is supplied to passage 50, the sameentering through the openings ll as the valve rotates. At the oppositeend of passage 45 a pair of outlet ports &3 are located, the same beingpositioned diametrically of the distributor valve 33. In accordance withthe invention the diametrical outlet ports are adapted to align withcertain conduits or passages formed in the housing and which conduct thelow pressure oil to the differential piston, which structure will bepresently described in detail.

Referring again to the distributor valve, the outlet end-of the same isalso provided with an internal passage 44 having openings 45 whichcommunicate with the chamber 45 connecting with the outlet 3d. The lowpressure oil from said passage 35 is accordingly discharged throughopenings 45 and the same leaves the housing In by the outlet line 3i.The passage Mi also has a pair of ports 47 which, as regards this end ofthe valve, function as inlet ports, the same being positioneddiametrically and aligning with certain conduits or passages in thehousing, which conduct the low pressure oil from the diiferentialpiston. The diametrical position of the outlet ports 47 transversely ofthe valve 38 is at right angles to the inlet ports 43, Figure 7.

The diiferential piston is located within the housing below the valve 38and includes a center piston 58 of large diameter positioned within thechamber '55 and having reciprocating movement in said chamber from endto end since the chamber has a length somewhat greater than that of thepiston 48. An extension is provided on each end of piston 48 and theseform the high pressure pistons, the one on the right hand end, Figure 1,being indicated 5!, and the piston 0n the left hand end being indicated52. It will be seen that the high pressure pistons are much smaller indiameter than the center or low pressure piston, the ratio of theirdiameters determining the pressure ratio between the low and highpressure oil. For example, if the high pressure pistons have a diameterand thus an area which is onefifth that of the large piston, then thehigh pressure oil will have a pressure which is approximately five timesthat of the low pressure oil. However, the volume of the high pressureoil will be one-fifth of that of the low pressure oil delivered to, thetransformer. It will be seen that the chamber for piston 48 is providedby the central unit II. The inlet unit 12 provides a chamber 53 for thehigh pressure piston 52, whereas, the outlet unit I3 in a similar mannerprovides chamber 54 for the high pressure piston 52, Figure '7.Cushioning or shock absorbing members 55 are located at the respectiveends of the chamber 50 to cushion the movement of the piston 48 at eachend of its stroke, the members being backed by the coil springs 55.

Chamber 53, accommodating the high pressure piston 5 I, hascommunication with a vertical bore 51, Figure 1, formed in the inletunit 12 0f the device. This bore has connection with a duct which willbe presently described by which it is supplied with low pressure oil andfor controlling the inlet of this low pressure oil to chamber 53 thevertical bore is equipped with an insert 58 containing a ball checkvalve 65 which opens to admit the low pressure oil and closes to preventits flow except through openings 6! which deliver into chamber 53 wherethe low pressure oil acts against piston 5i and is in turn acted on bysaid piston.

The base of vertical bore 51 is somewhat enlarged to receive anotherinsert 62 providing the ball check valve 63, which, however, opensdownwardly to admit high pressure oil from above and closes to preventits flow except through openings 64 in the said insert and which thusdelivers the high pressure oil to a longitudinal passage or duct 65having communication with the ball valve 63 through said openings. Theball check valves and 63 are so constructed and tensioned by theirassociated coil springs that valve 59 will open when subjected to lowpressure oil and valve 631 will open only when subjected to highpressure 01.

The outlet unit I3 is likewise provided with a vertical bore 66, similarto 51, and which has connection with a duct to be described, by whichthe bore is supplied with low pressure oil at definite times in therotary movement of the distributor valve 38. For controlling the inletof this low pressure oil to chamber 54 the vertical bore is equippedwith an insert 61 providing the ball check valve 68 which opens to admitsaid oil and closes to prevent its back flow so that the oil flows outthrough openings 69 into chamber 54 where it acts on piston 52 and is inturn acted on by said. piston. The base of vertical bore 66 is enlargedto receive another insert 15 providing ball check valve H. The valve H,however, opens downwardly to admit high pressure oil from above andcloses to prevent flow except through openings 12 in the insert. The oilflowing through openings 12 is admitted to the duct communicatingtherewith and the said duct 65 extends through and beyond the verticalbore 66 to connect with the vertical passage 13 comprising the highpressure oil outlet of the hydraulic transformer. This outlet connectswith the high pressure oil line 32, as shown in Figure 1. As regards theball check valves 68 and II, it is also understood that they areconstructed and tensioned by their coil springs to open when subjectedto low pressure oil and high pressure oil, respectively,

The various ducts or passages provided by the hydraulic transformer andwhich conduct low pressure oil from the distributor valve 38 to therespective ends of the differential piston will now be described. Theseducts are best shown in the schematic arrangement of Figure 7. Thecentral unit l I of the device adjacent the end toward the inlet unit I2is formed with a long vertical duct Hi and a short vertical duct 15, thesame being positioned on opposite sides of the longitudinal center ofthe device. Both ducts 14 and 15 have openings 16 and 11, respectively,communicating with the right hand end of chamber 50, Figures 1, 2 and 7.The vertical duct 14, which extends above the distributor valve on theright hand side of the same, Figure 2, connects at its upper end with ahorizontal duct 18, and said duct in turn connects with an inlet passage80 and an outlet passage 8i, the same having an inclination of aboutforty-five degrees and extending to the distributor valve 38. It will beunderstood that the passages 88 and 8| are positioned so as to alignwith the ports 43 and 41 spaced lengthwise of the distributor valve. Thevertical duct 15 connects at its upper end with a horizontal duct 82which at one end connects with an inlet passage 83 and an outlet passage84. The passages 83 and 84 extend to the distributor valve and the sameare positioned to align with ports 43 and 41, respectively. 'Also saidpassages have a forty-five degree inclination and are substantially inopposed relation to passages 80 and 8! previously mentioned. Theopposite end of horizontal duct 82 has connection with a vertical duct85 forming an extension of the same and which duct communicates with thevertical bore 51, Figures 1 and 4.

A similar arrangement of ducts and passages are provided for the lefthand end of chamber 58, as will be clear from Figures 3 and 7. The longvertical duct 86 and the short vertical duct 8'?! are reversed withrespect to the ducts '14 and 75. However, openings are formed at theirlower ends, indicated by numerals 88 and '89, respectively, and whichcommunicate with the left hand end of chamber 50. The long vertical duct86 connects at its upper end with a horizontal duct M, which in turnconnects with an inlet passage 9i and an outlet passage 92, the passagesaligning with the ports 43 and 41 and extending to the distributorvalve. The short vertical passage 81 on the opposite side of thedistributor valve 38 has connection at its upper end with a horizontalduct 83 which at one end connects with an inlet passage 94 and an outletpassage 95. These passages are inclined forty-five degrees and extend tothe distributor valve, being aligned with ports 43 and ll and insubstantial opposed relation with 9! and 92. It will also be observedthat each set of inlet and outlet passages are disposed around thedistributor valve in spaced relation of approximately ninety degrees Sothat with each quarter turn of the valve a difierent set of passages arealigned with the inlet and outlet ports t3 and 41. The end of thehorizontal duct '93 has connection with a duct 96 which leads in 6 adownward direction similar to 8 5 and communicates with the verticalbore 66.

This completes the arrangement of ducts and passages connecting thedistributor valve with the differential piston in accordance with theinvention and the operation of the parts for each half revolution of thevalve will be explained.

Referring to Figure '7, it will be understood that low pressure oil fromline 30 will have entered the distributor valve 38, that is, the inletpassage Lid of the valve through openings 41, and assuming the valve tobe positioned, as shown in Figure 7, the low pressure oil Will bedelivered by ports it to the inlet passages and 83 which are alignedwith the ports. This flow of oil is conducted by the ducts M and 15 tothe right hand end of chamber 58, the same entering this end of thechamber through the openings 16 and ll, respectively. The piston 48 islocated at the right hand end of chamber 58 and thus the low pressureoil acts on the piston to cause it to move in a direction toward theleft. The oil is also conducted by ducts 82 and 85 to the vertical bore5'1, the oil entering the insert 58 through the check valve til whichopens to admit flow of the oil in this direction. As previouslyexplained, this low pressure oil will enter chamber 53 and act on piston55 so that the full area of the differential piston is subjected topressure exerted by the low pressure oil and it accordingly moves to theleft end of chamber 58.

As piston moves to the left the oil in chamher 5% in front of piston 48is caused to flow out through the openings 88 and 89 into ducts 86 and8'? which deliver the oil to the outlet passages 92 and 95. Thesepassages, at this instance in the rotary movement of the valve 38, .arein alignment with the ports 4! so that the oil enters the valve 38 andsubsequently is delivered to the outlet 39 which returns this lowpressure oil to the reservoir, Figures 7 and 8.

The oil in front of the high pressure piston 52 is acted on by saidpiston as the same moves toward its extreme left hand position and thisoil is compressed to a high pressure. Assuming the area of piston 52 tobe one-fifth of the crosssectional area of piston 58, then the oil willbe increased in pressure five times that of the low pressure oil but itsvolume will be only one-fifth of the volume of oil acting on thedifferential piston and causing it to move to the left and compress theoil to its high pressure. This high pressure oil from chamber 54 iscaused to ilow into insert 'lll through the ball check valve 'H whichopens to admit said oil flow and which is delivered to the outlet 73 andthus to the high pressure line 32.

The differential piston remains in position at the left end of chambers58 and 54 as the rotary valve 38 continues to rotate and upon rotationof approximately ninety degrees the ports 43 align with the inletpassages 93 and 94 so that low pressure oil is delivered to thesepassages. Since said passages connect with the ducts 86 and 87 the lowpressure oil is admitted by openings 88 and 89 to the left end ofchamber 58 Where it acts on piston 48 to cause the piston to move to theright. The oil is also conducted by ducts '93 and it to vertical bore 68and it enters insert El through the ball check valve 88 which opens toadmit flow in this direction. From the insert the oil enters the chamber54 to act on piston 52 to augment the action of the oil on piston 38.

As the differential piston moves to the right the oil in front of piston48 is returned to ducts and T5 and delivered to outlet passages 8i and84 which at this instance are inalignment with the ports 41. This lowpressure oil enters the passage 44 in the valve '38 and is eventuallydelivered to line 3! and returned to the oil reservoir. The oil in frontof piston 5| is compressed to the high pressure, as previouslyexplained, and is forced to enter insert 62, the ball check valve 63opening to admit this flow of high pressure oil. From the insert 62 theoil is delivered to duct 65 and then to outlet 13 and to the highpressure line 32.

The differential piston remains in position in the right hand end ofchambers 50 and 53 as the rotary valve 38 continues its rotation. Uponanother ninety degree turn of the valve the ports 43 will be caused toagain align with inlet passages 8B and S3 and the ports 47 with outletpassages 92 and 95. The operation first described is thus repeated andthe differential piston will be moved to the left as has been describedto compress the oil in front of piston 52. Thus the valve 38 in rotatingone hundred and eighty degrees has produced two strokes of thedifferential piston, or, in other words, two pumping strokes for highpressure oil. For a full revolution of the valve it follows that fourpumping strokes of the differential piston result.

From the foregoing it will be understood that the distributor valve 38functions as a control member for directing the flow of low pressure oilto the differential piston. For each ninety degree rotative position ofthe valve certain inlet passages are supplied with low pressure oil fromline 30 and certain. outlet passages are connected to the outlet line 3|for discharge of low pressure oil. The fluid medium which is elevated tothe high pressure for which the device is designed is acted on by thesmall diameter pistons 5i and 52. In the first instance this medium atlow pressure does its share of work in reciprocating the differentialpiston and then the same fluid medium is acted on by the piston beingcompressed to the high pressure and eventually discharged through theoutlet line 32.

The rotary distributor valve 38 requires very little power since thevalve is hydraulically balanced by the balanced oil pressure acting onit. Flow into the valve takes place symmetrically through the openingsQ! and is discharged in a similar manner through openings 45. Also thearrangement of the ports 43 and 47 is symmetrical so that the outflowand inflow of the low pressure medium is balanced and the load on thevalve is a minimum.

The hydraulic transformer delivers the high pressure 011 by the to andfro strokes or reciprocations of the double ended differential piston.As the said piston moves in one direction, due to low pressure oilbehind it, the high pressure piston on the forward end is compressingoil to a high pressure. It follows that when the differential pistonreaches the end of its stroke in one direction, the flow of both highand low pressure oil will momentarily cease. If it were not for theauxiliary piston assembly 28, Figures 5, 6, 7 and 8, the low pressureoil would rise in pressure if the latter exceeds the pressure resistanceopposed against this fiow and the high pressure oil would drop inpressure. As the low pressure oil tends to rise in pressure betweenstrokes of the differential piston, the large end 98 of the auxiliarypiston is acted on by this now slightly higher low pressure oil. Saidlow pressure oil, due to its somewhat higher pressure, acts on the largeend 98 of the auxiliary piston to move the piston in a direction towardthe right, Figur 6, causing the coil spring I00 to be compressed and thesmall piston end llll to displace an amount of oil sufiicient to augmentthe high pressure oil in lines 32 and 33, which has ceased to flow fromthe transformer.

The auxiliary piston will function at each reversal in the movement ofthe differential piston. The area ratio of the large piston end 98 andthe small piston end [0! is actually the same as the area ratio of thedifferential piston. The function of the coil spring 500 is to returnthe piston 98 to its normal position, as shown in Figure 6, after it hasmade the movement as described, which is necessary to assure even flowof high pressure oil during reversals in the strokes of the differentialpiston.

The invention is not to be limited to or by details of construction ofthe particular embodiment thereof illustrated by the drawing as variousother forms of the device will of course be apparent to those skilled inthe art without departing from the spirit of the invention or the scopeof the claims.

What is claimed is:

1. In a hydraulic booster, a housing member having an inlet passageconnectin with a source of fluid pressure, an exhaust passage connectingwith an exhaust line, and a high pressure delivery line connecting withan outlet passage for a high pressure fluid, a differential pistonwithin the member mounted thereby for reciprocating movement, saiddifferential piston including a main operating piston havingreciprocating movement within a chamber provided therefor by said memberand ram pistons extending from each end of the main piston and whichmove in chambers respectively also provided by said member, a passage inthe member associated with each ram piston chamber at the end thereofand connecting with said outlet passage, a distributor valve journalledby said member for rotation and extending in an axial direction from theinlet passage to said exhaust passage, control ports provided by thevalv and connecting with the inlet passage, other control ports providedby the valve and connecting with the exhaust passage, a plurality ofducts formed in the member and having associated relation at one endwith the said control ports respectively, and at their other ends havingconnection with certain ends of the operating piston chamber, andcertain of said ducts having connection with the end of the ram pistonchambers respectively.

2. In a hydraulic booster, a housing member having an inlet passageconnecting with a source of fluid pressure, an exhaust passageconnecting with an exhaust line, and a high pressure delivery lineconnecting with an outlet passage for high pressure fluid, adifferential piston with the member mounted thereby for reciprocatinmovement, said diiferential piston including a main operating pistonhaving reciprocating movement within a chamber provided therefor bysaidports-provided by the valve, being located diametrically of the sameand connecting with the inlet passage, other control ports provided bythe valve, being located diametrically of the same but displaced ninetydegrees with respect to the first mentioned control ports and connectinwith the exhaust passage, a plurality of ducts formed in the member andhaving associated relation at one end with the said control portsrespectively, and at their other ends connecting with certain ends ofthe operating piston chamber, and certain of said ducts havingconnection with the end of the ram piston chambers respectively.

3. A hydraulic booster as defined by claim 1 additionally including acheck valve adjacent and in communicating relation with the end of eachram piston chamber between the same and the passage associatedtherewith.

4. An hydraulic booster as defined by claim 1 additionally including apair of check valves in spaced relation adjacent each ram piston chamberand in communicating relation therewith, one check valve in each pairbeing located between its respective chamber and the duct connectingtherewith, and the other check valve of each pair being located betweenits respectiv chamber and the passage associated therewith.

5. In a hydraulic booster, a housing member having an inlet passageconnecting with a source of fluid under pressure, an exhaust passageconnecting with an exhaust line, and an outlet passage connecting with ahigh pressure delivery line, a diiferential piston within the membermounted thereby for reciprocating movement, said differential pistonincluding a main operating piston having reciprocating movement within achamber of greater length than the same and provided therefor by saidmember, and including ram pistons extending from each end of the mainpiston and which move in chambers respectively also of greater lengththan the respective ram piston and provided therefor by said member, apassage formed in the member for each ram piston chamber havingconnection with the end of its ram piston chamber and connecting withthe outlet passage, each said passage delivering fluid to the outletpassage after compression of the same to a high pressure by its rampiston, at least one duct formed in the member for each ram pistonchamber and connecting with the end of the same for admitting the fluidunder pressure to the chamber, other ducts in the member havingconnecting relation respectively with the ends of the main pistonchamber for alternately admitting and exhausting said pressure fluidwhereby to produce reciprocating movement of the main operating pistonand said ram pistons, and means controlling the admission of thepressure fluid to said ducts for delivery to the ram piston chambers andmain operating piston chamber and exhausting of the pressure fluid fromthe latter chamber, said means including a distributor valve journalledby the member and having control ports connecting with the inlet passageand other control ports connecting with the exhaust passage.

6. An hydraulic booster as defined by claim 5 additionally including acheck valve adjacent and in communicating relation with the end of eachram piston chamber between the same and the passage for said chamber.

7. A hydraulic booster as defined by claim 5 additionally including apair of check valves in spaced relation adjacent each ram piston chamberand in communicating relation therewith, one check valve in each pairbeing located be- 10 tween its respective chamber and the ductconnecting therewith, and the other check valve of each pair beinglocated between its respective chamber and the passage for said chamber.

8. In a hydraulic booster, in combination, a differential piston mountedfor reciprocating movement, said piston including a main operatingpiston and a ram piston extending from each end of the said main pistonand of less diameter than the main piston, a main piston chamber and rampiston chambers associated therewith, said main and ram pistons havinglocation within said chambers respectively, each ram piston chamberextending from its end of the main piston chamber, mechanism foreffecting reciprocating strokes of the diiferential piston includingmeans for delivering a fluid under pressure to either end of the mainpiston chamber, means for simultaneously discharging the fluid from theopposite end of the chamber, and means for also delivering a fluid underpressure to the respective rear ram piston chamber behind the ram pistonthereof, whereby the forward ram piston is caused to compress the fluidwithin its chamber to a pressure higher than the initial pressure of thefluid, said mechanism including a rotary distributor valve having acontrolling operation by reason of its rotation for controlling thedelivery to and discharge from the various chambers of said fluid underpressure.

9. In a hydraulic booster, in combination, a differential piston mountedfor reciprocating movement, said piston including a main operatingpiston and a ram piston extending from each end of the said main pistonand of less diameter than the main piston, a main piston chamber and rampiston chambers associated therewith, said main and ram pistons havinglocation within said chambers respectively, each ram piston chamberextending from its end of the main piston chamber, a pair of checkvalves at the outer end of each ram piston chamber for controlling thedelivery to and exit from said chamber of a fluid, mechanism foreffecting reciprocating strokes of the differential piston includingmeans for delivering a fluid under pressure to either end of the mainpiston chamber, means for simultaneously discharging the fluid from theopposite end of the chamber, and means for also delivering a fluid underpressure to the respective rear ram piston chamber behind the ram pistonthereof, whereby the forward ram piston is caused to compress the fluidwithin its chamber to a pressure depending on the setting of the checkvalue controlling the exit of the fluid from the chamber, said mechanismincluding a rotary distributor valve having a controlling operation byreason of its rotation for controlling the delivery to and dischargefrom the various chambers of said fluid under pressure.

10. In an hydraulic transformer having an inlet for supplying a lowpressure oil thereto, a low pressure oil outlet, and a high pressure oiloutlet for delivering oil at a higher pressure, a double endedreciprocating piston provided by said transformer for pumping said highpressure oil by the to and fro strokes of said piston, whereby the flowof both high and low pressure oil momentarily ceases when thereciprocating piston reaches the end of its stroke in either direction,and an auxiliary piston assembly for counteracting any rise in pressureof the oil in the low pressure oil inlet and any drop in pressure of theoil in the high pressure oil outlet caused by said stoppage in the flowof 011, said auxiliary piston assembly having 11 connected relation withboth the low pressure oil inlet and the high pressure oil outlet andincluding a double-ended piston having a large diameter end and a smalldiameter end and subjected to the low and high pressure oil at the endsrespectively.

11. In an hydraulic transformer having an inlet for supplying a lowpressure oil thereto, a low pressure oil outlet, and a high pressure oiloutlet for delivering oil at a higher pressure, a double ended,differential piston mounted for reciprocation by said transformer forpumping said high pressure oil by the to and fro strokes of said piston,whereby the flow of both high and low pressure oil momentarily ceaseswhen the reciprocating piston reaches the end of its stroke in eitherdirection, and an auxiliary piston assembly for counteracting any risein pressure of the oil in the low pressure oil inlet and any drop inpressure of the oil in the high pressure oil outlet caused by saidstoppage in the flow of oil, said auxiliary piston assembly havingconnected relation with both the low pressure oil inlet and the highpressure oil outlet and including an auxiliary piston having a largediameter end subjected to the low pressure oil and a small diameter endsubjected to the high pressure oil, and said auxiliary piston having anon-pumping action.

12. In an hydraulic transformer for increasing the pressure of a fluidmedium delivered thereto and wherein the volume of the high pressuremedium compared to the volume of the low pressure medium entering thedevice is inverselyproportional to the boost in pressure, thecombination with an inlet and an outlet for the low pressure medium, anoutlet for said high pressure medium,

a reciprocating double ended piston for pumping said high pressuremedium by the to and fro strokes of the same, an auxiliary pistonassembly having connected and operative relation with both the lowpressure inlet and the high pressure outlet, said auxiliary pistonassembly having operation at each reversal in the movement of the doubleended pumping piston to maintain an even flow of the high pressuremedium from said high pressure outlet said auxiliary piston assemblyincluding an auxiliary piston having a large diameter end and a smalldiameter end, the large diameter end of said piston having associatedrelation with the inlet and being subjected to the low pressure medium,the small diameter end having associated relation with the outlet andbeing subjected to the high pressure medium, and said auxiliary pistonhaving a non-pumping action.

JOHN C. HANNA.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 38,531 Coates et a1 May 12, 1863617,934 Mason Jan.'17, 1899 1,377,585 Johanson May 10, 1921 2,053,543Vincent Sept. 8, 1936 2,239,727 Mayer Apr. 29, 1941 FOREIGN PATENTSNumber Country Date 285,985 Italy May 28, 1931

